# Compressive Failure and Dual-Defect Coupling Effects of Open-Hole Composite Laminates with Drilling-Induced Delamination

## TL;DR

This study examines how drilling-induced delamination affects the compressive strength of carbon fiber composites with open holes and explores failure mechanisms under dual defects.

## Contribution

The novelty lies in analyzing dual-defect coupling effects and revealing a unique failure mode in opposite-side delamination scenarios.

## Key findings

- Dual delamination defects significantly reduce compressive load-bearing capacity in open-hole composites.
- Opposite-side defects cause dual-crack propagation, leading to lower compressive strength than same-side defects.

## Abstract

This study investigates the influence of drilling-induced delamination damage on the compressive mechanical behavior of open-hole carbon fiber-reinforced composite laminates and explores the failure mechanisms under dual-defect coupling effects. Specimens with circular delamination defects of varying sizes were fabricated by embedding polytetrafluoroethylene (PTFE) films during the layup process. Ultrasonic C-scan and digital image correlation (DIC) techniques were used to monitor delamination propagation and deformation behavior. A cohesive zone-based numerical model was developed and validated against experimental results to reveal the three-stage failure process in single-defect cases. The validated model was then used to analyze the coupling effects of dual defects (same side and opposite side). The results show that dual delamination defects significantly reduce the compressive load-bearing capacity of open-hole composite laminates. Specifically, same-side defects exhibit a failure mode similar to single-defect structures, while opposite-side defects display a unique failure behavior characterized by dual-crack propagation, further reducing the compressive load-bearing capacity.